80 



FIRST BOOK OF GRASSES 



(staminate or neuter) at each joint, the rachis dis- 

 articulating at the summit of each joint, this and the 

 pedicel of the sterile spikelet remaining attached at 



their base to the per- 

 fect spikelet as a pair 

 of little stalks. In 

 this group of grasses 

 specialization consists 

 chiefly in modifications 

 of the axes of inflores- 

 cence and secondarily 

 in the modification of 

 the spikelets. In Fig. 

 73, A (Johnson-grass, 

 Holcus halepensis) , are 

 two views of a single 

 joint, consisting of the 

 sessile perfect spikelet 

 with the attached ra- 

 chis joint and the ped- 

 icel with its staminate 

 spikelet. Fig. 73, B, is 

 a diagram of a raceme 



FIG. 73, A, two views of single joint of four SUCh joints and 



of raceme of Holcus halepensis; B, 73 Q a diagram of the 

 diagram of raceme of four joints; , . .. ,. . , 



C, diagram of rachis and pedicels; D, raCfllS and pedicels, trie 



inflorescence. spikelets removed and 



the points of disarticulation shown by dotted lines. 

 In sorghum, or Holcus, these little racemes are borne 

 on the ultimate branchlets of a panicle (Fig. 73, D). 



